1. Field of the Invention
The present invention relates to flow meters, and more specifically to flow meters with self-illuminating floaters.
2. Description of the Related Art
It is frequently necessary in an industrial setting to measure the flow of fluids through pipes. For example, in bulk processing of compounds in chemical plants the amount of various fluids being introduced into a reaction vessel must be determined and controlled. In plant operations requiring pressurized air or steam it is often desirable or necessary to monitor consumption of these fluids. In other instances, the supplier of a working fluid or fuel desires to know the quantity of fluid delivered in order that an appropriate fee may be charged. A number of fluid flow measuring devices are currently known.
The most commonly used fluid flow metering devices can be generally categorized as belonging to one of the following groups.
Positive displacement meters function by receiving and discharging discrete volumes of fluid through, for example, a reciprocating piston in a cylinder. The number of cycles of such a device occurring in a unit period of time is proportional to the flow rate of fluid passing through the meter. Although accurate, positive displacement meters are mechanically complex and are highly sensitive to foreign matter contamination.
Obstruction type meters employ an orifice or other restriction in the fluid path and the flow rate is calculated from the measured pressure drop across the restriction. Those meters generally have limited measurement ranges and are highly sensitive to the flow patterns of the fluid passing therethrough. Moreover, obstruction meters provide instantaneous flow measurement, which must be integrated to evaluate total flow.
Rotating vane type meters are frequently used in measuring fluid flow. These meters function by causing the flowing fluid to impart a tangential force on an impeller causing rotation thereof. The rotational velocity of the impeller is related to volumetric flow rate.
Variable area flow meter provides a weighted member movably disposed across an orifice such that the position of the weighted member determines the orifice area. The weighted member provides an essentially constant fluid head against the fluid entering the system so that the displacement of the weighted member is essentially a linear relation with the rate of volumetric flow of the fluid.
The principal advantage of a variable area flow meter is that, at low cost, it provides a wide range of capacity with low system resistances and is essentially linear. One well-known and popular form of variable area flow meter, often called a rotameter and considered the closest analog to the present invention, is shown in FIG. 1. A flow meter 10 utilizes a floater 12 moving vertically within a tapered tube 14, usually transparent, whose area increases upwardly. A diameter 16 of the metering floater 12 in the rotameter 10 is slightly less than the minimum inside diameter 18 of the tube 14, so when the floater 12 is placed within the tube 14, any clearance between the floater 12 and tube 14 forms an annular orifice 20, a cross sectional area thereof varying in accordance with the position of the floater 12. In this type of rotameter, a weighted floater 12 contained in an upright tapered tube 14 is raised to a position of equilibrium between the downward gravitational force of the floater 12 (symbolically shown by an arrow 22) and the upward force of the fluid flowing past the floater 12 through the annular orifice 20 surrounding the floater 12, which force is symbolically shown by arrows 24. This position of equilibrium is therefore a function of flow ratexe2x80x94the greater the flow rate, the higher the vertical position of the floater.
When the stream of fluid to be measured is made to enter the lower end 26 of the tube 14, it causes the floater 12 to rise to a height where its weight is just balanced by the pressure drop across the orifice 20. At the same time, the floater 12 rotates, and the very term xe2x80x9crotameterxe2x80x9d was derived from the fact that floaters have slits (like those with reference numeral 28 in FIG. 1) to impart a rotational force thereto for the purpose of centering and stabilizing the floater. The tube 14 is typically made of glass or other suitable materials imprinted with a graduated scale 30 such that the position of the floater 12 may be correlated with flow rate of the particular fluid under test. High sensor 32 and low sensor 34 may be installed outside the tube to catch the highest and lowest permissible readings, 36 and 38, respectively.
A disadvantage of the rotameter described in the above is that visual reading the results of the tests is infrequently difficult since the graduated scale 30 may not be clearly visible because of absence of outer lightxe2x80x94in dark periods of a day or when the flow meter is placed, say, under a machine. Another reason for the visual reading to be impaired is particles in the flow that may cause fouling and/or scaling of the tube 14. These reasons may cause either misreading the results or make reading impossible at all.
Therefore, the object of the present invention is to provide a flow meter that, while possessing the advantages of the flow meters known in the art, would be free of their disadvantages.
One more object of the invention is to provide a flow meter with easily readable metering results.
Still one more object of the present invention is to provide a flow meter with a self-illuminating floater.
According to the present invention, providing a variable area flow meter that comprises a housing and a floater therein attains the above objects. The housing is placed inside a U-shaped permanent magnet, and the floater includes a rotor coil. Connected to the rotor coil is a DC bulb. An ascending fluid flow rotates the floater. The rotation of the floater with the rotor coil in the magnetic field of the permanent magnet causes a direct current to flow through the bulb. Light from the bulb makes it easier to read the results of metering.